My Hydrogen-Powered Car Averages 40+ MPG, but I Want More

Finally crunching the numbers after the three-month lease of a lifetime with GM's Chevy Equinox, PM's Citizen Fuel Cell reports the good news on mileage (between 33 and 55 mi/kg of hydrogen, with an average of 41) and the bad (squeezing out the last "drop" of hydrogen, with tough MPG equivalent measurements). But now that his real-world, long-term test has proved fuel cells can, indeed, double the fuel economy of your average gasoline-powered car, the future of hydrogen isn't looking so bad after all.

NEWPORT BEACH, Calif. -- After driving a hydrogen-powered car around for GM's Project Driveway test fleet for three months--first receiving the keys, then getting used to it and eventually begging for more fill-er-ups--I can finally appreciate what's it like to live free from gasoline. Even as oil prices have dipped recently, gas is still raging above $4 per gallon, and everyone has probably done some math to figure out how much you'd save buying a more fuel-efficient car. Well, I've told you that my prototype Chevrolet Equinox is fun to drive, and you know it doesn't pollute, but here's the bottom line: Over time, this alt-fuel car gets really good mileage.

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The Equinox runs on hydrogen, not gasoline, so for the time being there is no wild fluctuation in the fuel price. And that's comforting. Sure, oil companies may eventually sell hydrogen and influence pricing in some way. But hydrogen is something we can make in our own backyards, right here in the United States. And there is only water vapor coming out of that tailpipe, so you don't have to feel guilty about how much you drive. The "well-to-wheel" emissions for these cars are very low. And I like knowing that I'm not contributing to local air pollution.

Most important, however, these fuel cell vehicles are twice as efficient as the average gasoline car. Hydrogen filling is measured in kilograms (kg), so fuel economy is measured in miles per kilogram. And since there's approximately the same potential energy in 1 kg of hydrogen as there is in 1 gal. of gasoline, comparing by prototype's "mpkg" numbers to the mpg output of an internal-combustion vehicle is roughly equivalent.

I've mentioned before just how much pickup the Equinox has with its torquey electric motor. But like all vehicles, economy is still very dependent on how hard you drive, and what kind of fuel-efficiency tricks you pull behind the wheel. On a gasoline vehicle, you typically get your best mileage between 50 and 60 mph, which turns out to be similar for a fuel cell car. Full throttle acceleration, although fun, makes a big impact on fuel economy. The Chevy Equinox has a kilowatt gauge on the dashboard that replaces the tach, so you can keep tabs on the energy being consumed.

Over three months, through about 35 fill-ups, I've kept pretty darn good track of the mileage reading from the vehicle's trip computer. Without further ado, then, here's the breakdown of my hydrogen mileage, measured by the aforementioned mpkg, in chart form for the whole lease--and in a pretty interesting graph for the last eight weeks of driving:

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class="builtTable">

Chevrolet Equinox Fuel Cell Mileage

Date

Odometer

Miles

kg

Mi/kg

Comments

April 23

470

n/a

n/a

n/a

delivery

April 25

581

111

n/a

n/a

fill-up

April 28

726

145

n/a

45.20

fill-up

April 29

758

32

n/a

n/a

training

May 2

876

118

n/a

n/a

fill-up

May 4

914

38

n/a

n/a

top-off

May 6

1055

141

4.86

n/a

fill-up

May 8

1181

126

4.54

n/a

fill-up

May 13

1249

68

3.03

n/a

top-off

May 14

1308

59

2.64

n/a

top-off

May 15

1330

22

1.17

n/a

top-off

May 30

1553

223

3.97

37.70

GM service

June 3

1666

113

4.38

38.80

fill-up

June 8

1797

131

4.82

39.50

fill-up

June 9

1867

70

2.90

36.60

top-off

June 13

1989

122

1.75

39.50

error

June 13

2030

41

4.25

42.10

n/a

June 14

2156

126

3.95

43.60

GM facility

June 16

2347

191

4.39

45.20

n/a

June 19

2445

98

3.56

39.50

n/a

June 21

2586

141

n/a

45.20

error

June 22

2702

116

3.68

45.20

n/a

June 26

2834

132

4.80

40.70

n/a

June 30

2981

147

4.64

44.40

n/a

July 5

3109

128

1.16

37.70

error

July 5

3130

21

4.26

n/a

n/a

July 6

3234

104

3.70

40.10

n/a

July 7

3361

127

4.64

37.70

n/a

July 11

3499

138

4.04

42.10

error

July 12

3527

28

1.89

33.60

n/a

July 15

3671

144

3.41

43.60

error

July 17

3725

54

3.20

38.20

n/a

July 21

3871

146

4.81

42.90

n/a

July 22

4000

129

3.78

44.40

n/a

Overall Fuel Economy:

41.02 mi/kg

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Crunching the numbers (I'm a LASIK surgeon, not a mathematician), my average mileage came to just over 41 mi/kg. This data is mainly city driving, with some longer freeway trips on the weekends. During pure city driving, my spot checks were between 38 and 42 mi/kg And the results depended largely on how quickly I accelerated from stops. One caveat to this data is that it all comes from the onboard trip computer. Unfortunately, hydrogen fill-ups are very difficult to measure accurately when it's dispensed as a gas, due to fluctuations in temperature and pressure. Because of this, I can't accurately record exactly how many kilograms of hydrogen the car takes in at each fill-up. This is an issue that I've heard pump manufacturers and automakers are working on, and it will have to be fixed before hydrogen fill stations go mainstream. If I had that precise data, I would have calculated my fuel economy based on miles driven between fill-ups, then compared it to the onboard computer readings.

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Online, at GM's Project Driveway Web forums, many of us lessees have shared our fuel economy stats. From what I've been reading, several of the drivers on the East Coast are averaging in the mid-to-high 50s. I haven't been able to figure out what they are doing to get better gas mileage than those of us out west, but perhaps they have less heavy feet, or are just spending more time on the freeway. As I've found, freeway driving produces much better fuel economy.

My first long drive out of town was a 130-mile round trip--almost all freeway. Knowing that my Equinox was returning as low as mid-30s mi/kg in the city--and that I only had a 4.2 kg hydrogen tank--I became a little nervous about making the trek there and back. Any little side trip would risk running too low on hydrogen for the drive home--and I'd be stranded. So on that trip, I drove very conservatively on the freeway, trying to keep it around 70 mph, and resisted the urge to pass other cars. To my surprise, when I got back home the Equinox had almost a half-tank left, and said I was averaging over 55 mi/kg. I was impressed, and immediately started thinking about how I could get this exemplary fuel economy on a regular basis.

I have to give credit to the engineers who optimized the acceleration of the Equinox. With a normal application of the right pedal, you get a nice, even thrust. The kw gauge isn't linear to the pedal position; instead, the needle will jump to 80 kw or so to get you going, then decrease rapidly down to 10 or 20 kw for cruising once up to speed. The motor never feels like it's working hard, but with that big initial surge comes an expense to economy.

So I started watching the kw gauge a lot--probably too much. It's not exactly the safest practice, but it becomes quite addictive trying to eke out any extra mileage you can. Upon initial acceleration, if I kept the gauge at around 20 kw, progress was slow. But then again, I was only using about one-quarter of the normal takeoff power. And that made me think that GM could offer the consumer a few more buttons and dials, so one could bias economy over high performance by just limiting the power output. Holding the gas pedal at the right spot to control the power is difficult, but a dial or setting that could do it for you would be easy. And it would basically let you set the vehicle to return the best mi/kg. For comparison, cruising on the freeway at 75 mph on flat pavement only takes about 20 kw. So if you can handle a little delay in getting up to speed, the fuel cell system could certainly be tuned for even better economy.

GM's goal with these vehicles, however, wasn't to see how much mileage they could squeeze out of each tank. Instead, they chose a middle ground of performance with an acceptable range to prove out the vehicle and technology, and I think they made a good choice. The settings make for a fun car to drive, while still returning about double the fuel economy of an average gasoline vehicle. Make no mistake: Fuel cell technology is still in its infancy. But GM already has the next-generation fuel cells in its lab, so I believe we've got a lot of room for improvement over the next couple of years. And from where I sit, this is an excellent start.